JP2009004271A - Battery case - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat rectangular battery case made of an aluminum alloy, and provided with an explosion-proof mechanism allowing accuracy of remaining thickness of a thin part to be easily secured, and cleaving before being ruptured by increase of internal pressure. <P>SOLUTION: This battery case is characterized in that a recessed part 6 of which the outline is a closed curve in a plan view is formed nearly at the center of a side surface 32 being a small-width surface of a battery case body; a groove part 5 generally-analogous to the recessed part 6 is formed along the recessed part 6; and buckling distortion is generated in the recessed part 6 when the internal pressure is increased to exceed a predetermined value, and thereby the groove part 5 is ruptured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a battery case having an explosion-proof mechanism that releases a predetermined internal pressure when the internal pressure is applied.

  Lithium ion secondary batteries are widely used as power sources for mobile phones, notebook personal computers, and the like. The case that is the exterior of the secondary battery (hereinafter referred to as the battery case) may have an internal pressure that increases due to the charging / discharging of the battery or a temperature increase in the usage environment. Has the risk of bursting. In order to prevent such rupture of the battery case, an explosion-proof mechanism is provided in which a part of the battery case is ruptured to release the internal pressure with an internal pressure that does not rupture.

  A general explosion-proof mechanism is obtained by thinly processing a part of a plate material constituting a battery case into a groove shape, and selectively breaking and cleaving the groove with a small increase in internal pressure. Further, metal is often used for the plate material constituting the battery case. Patent Documents 1 to 3 disclose a battery case using an iron alloy such as SUS and Patent Documents 4 to 7 using an aluminum alloy. ing.

As a method of thinning a part of the plate material, Patent Documents 1 and 2 describe a method of bonding a plate material having a through hole and another plate material, and Patent Document 3 discloses a cold forging method using a die and a punch. And the methods by press working are disclosed in Patent Documents 4 to 7, respectively. In addition, as the shape of the thin portion, in a plan view, Patent Documents 2 and 5 include a single straight line, and Patent Documents 1, 4 and 6 include a plurality of straight lines that intersect at one or more points such as a cross shape. 3 and 7 are annular and various shapes are disclosed. Patent Documents 1 and 2 are the lid (sealing plate), Patent Documents 4 and 5 are the main body wide surface, and Patent Document 6 is the main body wide surface or the main body narrow surface. Further, Patent Document 7 is assumed to be provided as an internal partition rather than an exterior.
JP-A-5-314959 (paragraphs 0015 to 0020, FIG. 4) JP 2002-83578 A (paragraphs 0007 to 0008, FIG. 2) Japanese Patent Laying-Open No. 2005-251447 (paragraphs 0016 to 0023, FIG. 4) Japanese Patent Laid-Open No. 2001-35467 (paragraphs 0024 to 0032, FIG. 1) JP 2001-345083 A (paragraphs 0026 to 0029, FIG. 2) JP 2001-143664 A (paragraphs 0019 to 0021, FIGS. 1 and 5) JP-A-11-204093 (paragraphs 0015 to 0020, FIG. 1)

  In order to surely tear the battery case before it ruptures, it is essential to ensure the accuracy of the remaining thickness of the thin portion. In the above-described prior art, it is difficult to secure the accuracy of the remaining thickness of the thin portion by the method of bonding a plurality of plate materials by thermocompression bonding or the like or the method of cold forging. Here, as a plate material constituting the battery case, the aluminum alloy is excellent in workability, weight reduction and cost, but because it is soft, the thin part is broken without excessively deforming other parts of the main body. For example, in Patent Documents 2 and 7, the thickness is as extremely thin as 30 μm, and accordingly, the difference from the original plate thickness is increased, and the amount of processing by thin wall processing is large. Such thin-wall processing is difficult to accurately process the remaining thickness of the thin-walled portion even if it is press processing, particularly high-precision coining.

  Further, when the thin wall portion is provided on the wide surface of the battery case body, the wide surface is gradually deformed as the internal pressure rises due to the softness of the aluminum alloy, so that a considerable amount of internal pressure needs to be increased until it breaks. In addition, when it is provided on the side surface which is a narrow surface, a wide thin portion for receiving a large amount of internal pressure is required, and a long thin thin portion along the long side is formed. It is necessary to perform with high accuracy. On the other hand, when the thin portion is provided on the lid of the battery case, it is necessary to avoid the terminal and the electrolyte injection port provided on the lid, and therefore the position of the thin portion is restricted by the specifications of the battery. In addition, since the lid plate is thicker than the main body, it is necessary to increase the processing amount by thin-wall processing or to separately manufacture and insert an explosion-proof mechanism.

  The present invention has been made in view of the above problems, and provides an aluminum alloy battery case including an explosion-proof mechanism that is easy to ensure the accuracy of the remaining thickness of the thin-walled portion and reliably ruptures before rupture. With the goal.

  In order to solve the above problems, the present inventors have provided an explosion-proof mechanism on the side surface, which is a narrow surface of the battery case body, which is less likely to be deformed compared to the front and back surfaces that are wide surfaces with a small load. The idea has been to provide a thin-walled explosion-proof mechanism that can accommodate a thin-walled processing region in a central part where deformation stress tends to concentrate on the side surface.

  That is, the battery case according to claim 1 is a sealed battery case provided with an explosion-proof mechanism that partially ruptures when the internal pressure rises and exceeds a predetermined value. It is a flat rectangular parallelepiped whose rear surface is wider than the side surface and the bottom surface, and includes a lid formed from the upper surface and a main body composed of five surfaces other than the upper surface, and the main body is a narrow surface thereof It has a breaking groove formed in the approximate center of a side surface or the bottom surface, and the breaking groove is formed in a closed curve including a curve or a part of a curve, or a discontinuous closed curve in which a part of the closed curve is discontinuous. The explosion-proof mechanism is used.

  In the battery case configured as described above, when the internal pressure rises and the wide surfaces facing each other swell in a direction away from each other, the side surface is drawn toward the ridge line (long side) with the wide surface, and deformation stress is concentrated on the side surface. When the easy approximate center is deformed including the breaking groove formed therein and the internal pressure further rises, the deformed breaking groove is easily broken to release the internal pressure. In addition, unlike a cover having a relatively large plate thickness, the amount of processing by thin wall processing is small.

  Furthermore, the battery case according to claim 2 is the battery case according to claim 1, wherein a recess surrounding the breaking groove is formed on the side surface or the bottom surface.

  In this way, by forming a step due to the recess in the vicinity of the periphery of the fracture groove, buckling deformation occurs in the recess due to an increase in internal pressure, so the side surface is easily bent at this portion, and the fracture groove is more reliably secured. Break.

  Furthermore, the battery case according to claim 3 is the battery case according to claim 1 or 2, wherein the breaking groove is formed at the first breaking groove and at the bottom of the first breaking groove. It consists of a second breaking groove, and the bottom of the second breaking groove is the bottom of the breaking groove.

  Thus, by making the breaking groove part into a two-stage structure of the first breaking groove and the second breaking groove formed at the bottom thereof, the remaining thickness of the bottom part of the second breaking groove which is the thinnest part is reduced. It becomes easy to process with high accuracy.

  Furthermore, the battery case according to claim 4 is the battery case according to any one of claims 1 to 3, wherein the breaking groove portion of the discontinuous closed curve includes a continuous portion at least half of the closed curve. To do.

  Since the breaking groove portion having such a shape has a continuous groove portion that is at least half of the closed curve, it is easy to break due to deformation of the battery case.

  The battery case according to claim 5 is the battery case according to any one of claims 2 to 4, wherein the main body is made of an aluminum alloy plate having a proof stress of 200 to 300 MPa, and is a thinnest portion that is a bottom portion of the breaking groove portion. The remaining thickness is 40 to 70 μm, and when the internal pressure is 0.4 MPa or less, buckling deformation occurs in the concave portion, and the breaking groove portion breaks.

  In this manner, by controlling the yield strength of the material constituting the main body and the remaining thickness of the thin portion, an explosion-proof mechanism that can be reliably cleaved at a predetermined internal pressure can be obtained.

A battery case according to a sixth aspect is the battery case according to the first to fifth aspects, wherein the main body is made of a 3000 series aluminum alloy plate.
By applying such a material, a battery case that can be easily processed and has high corrosion resistance can be obtained.

The battery case according to the present invention has the following excellent effects.
When the internal pressure of the battery case becomes equal to or higher than a predetermined value, the fracture groove that is an explosion-proof mechanism can be opened to release the internal pressure. In addition, since the shape of the groove portion is a closed curve or a discontinuous closed curve, the thin-walled processing region can be reduced, and the thin-wall processing is easy because there are no corners.
Furthermore, the explosion-proof mechanism can be more reliably cleaved when the internal pressure becomes a predetermined value or more by forming the recess around the breaking groove.
Further, since the breaking groove portion has a two-stage structure, the remaining thickness of the breaking groove portion can be easily processed with high accuracy. In particular, since there is a recess around the breaking groove having a two-stage structure, when the internal pressure exceeds a predetermined value, the recess is buckled and the breaking groove is more reliably opened. Can do.
Furthermore, the thin-wall processing for forming the breaking groove is easy even with a soft aluminum alloy material or the like, and the recess is easy to process.

  Hereinafter, the best mode for realizing a battery case according to the present invention will be described with reference to the drawings. FIG. 1 is an external perspective view of a battery case, (a) is an external perspective view of a battery case according to an embodiment of the present invention, and (b) is an external perspective view of a battery case according to another embodiment of the present invention. is there.

  As shown in FIG. 1A, the battery case 1 is a flat, substantially rectangular parallelepiped formed of an aluminum alloy plate and having a front surface and a back surface that are wider than the side surface and the top and bottom surfaces. As for this battery case 1, the upper surface comprises the lid | cover 2, and the main body 3 is comprised by the other five surfaces. In the battery case 1, an explosion-proof mechanism 4 is formed in the approximate center of the side surface 32 that is the narrow surface of the main body 3.

  The shape of the battery case 1 is a flat, substantially rectangular parallelepiped composed of a front surface and a rear surface that are wide surfaces, a side surface that is a narrow surface, and upper and lower surfaces, but the size conforms to the specifications of the secondary battery.

  The main body 3 of the battery case 1 is a box having an open upper surface, and as a material thereof, for example, a 3000 (Al—Mn) -based aluminum alloy is preferable in terms of workability and corrosion resistance. Further, the material strength is preferably 200 to 300 MPa in order to be cleaved at an appropriate internal pressure. Further, the plate thickness of the main body 3 (corresponding to Tc in FIG. 2 (b)) depends on the specifications and processing method of the secondary battery, and is not particularly limited. Preferably, the bottom surface is 0.3 to 0.7 mm, The front and back surfaces are 0.15 to 0.25 mm. In addition, as a shaping | molding method of the main body 3, shaping | molding the aluminum alloy board of plate | board thickness of 0.3-0.7 mm by well-known methods, such as a drawing process, is mentioned, for example.

  Although the material which forms the lid | cover 2 is not specifically limited, The aluminum alloy plate of the same material as the main body 3 is preferable. Moreover, the plate | board thickness of the lid | cover 2 is based on the specification, processing method, etc. of a secondary battery, Although it does not specifically limit, Preferably, it is 0.7-1.5 mm. In addition, as a shaping | molding method of the lid | cover 2, well-known methods, such as press work, are mentioned, for example.

  FIG. 1B shows a battery case according to another embodiment of the present invention. The battery case 1A, like the battery case 1 (see FIG. 1 (a)), is a flat, substantially rectangular parallelepiped whose front and back are wider than the side and top and bottom, and the top constitutes a lid 2A. The main body 3A is composed of the five sides. However, while the battery case 1 is vertically long when viewed from the front, the battery case 1A is horizontally long when viewed from the front as shown in FIG. Therefore, in the battery case 1A, in the main body 3A, the bottom surface 32A is narrower than the side surface and has a larger aspect ratio, and the explosion-proof mechanism 4 is formed in the approximate center of the bottom surface 32A. Since other configurations are the same as those of the battery case 1, the description thereof is omitted. In the description of the explosion-proof mechanism 4 described later, the narrow surface is the side surface 32, but in the battery case 1A of the present embodiment, the bottom surface 32A is replaced.

  Next, the explosion-proof mechanism 4 in the battery case 1 will be described. 2A and 2B are schematic views of the explosion-proof mechanism according to the first embodiment. FIG. 2A is a plan view (partially enlarged view of a battery case), FIG. 2B is a cross-sectional view taken along line AA in FIG. These are sectional drawings of the modification of 1st Embodiment.

  As shown in FIG. 2 (a), the explosion-proof mechanism 4 of the present embodiment is provided at the approximate center of the side surface 32, which is the narrow surface of the main body 3 (see FIG. 1 (a)), and an oval groove ( (Breaking groove) 5. This groove part 5 is formed in the closed curve which includes a curve or a curve in part. Moreover, the groove part 5 is formed so that it may become thinner than the thickness of the side surface 32, as shown in FIG.2 (b). In the present embodiment, the portion around the groove portion 5 and the portion surrounded by the groove portion 5 are formed to be on the same plane.

  The remaining thickness Ts (see FIG. 2B) of the thinnest portion which is the bottom of the groove portion 5 is preferably 20 to 110 μm, and more preferably 40 to 70 μm in order to cleave with an appropriate internal pressure. It is. The width Ws of the thinnest portion is not particularly limited, but is preferably 10 to 100 μm from the viewpoint of workability and strength. The distance Ls from the long side of the groove 5 is not particularly limited because it depends on the width of the side surface 32 and the like, but is preferably 200 to 700 μm in terms of workability and strength. The groove 5 is preferably formed by press working such as coining.

  In the battery case 1, the side surface 32 including the groove portion 5 is a narrow surface and the two long sides facing each other are close to each other, so that deformation is less likely to occur compared to the front and back surfaces with a small load. On the other hand, the front side, which is the wide surface of the main body 3, will be described later in detail with reference to FIGS. 4 and 5 as the internal pressure increases, but the centers of the wide surfaces gradually swell in directions away from each other. Accordingly, the center of each side of the front and back surfaces is drawn, and the central part of the side surface 32 sharing the side as a long side is drawn inward. When the internal pressure further rises, the side surface 32 bends at the central portion where deformation stress (buckling, bending, compression, tension, etc.) tends to concentrate, and a part of the wide surface in contact with the bent portion is also buckled. Raises and deforms. As a result of such non-uniform deformation, the bottom of the groove portion 5 which is a thin wall portion formed in the groove portion 5 at the bent portion is easily broken to release the internal pressure.

  Next, a sectional view of a modification of the explosion-proof mechanism of the present embodiment is shown in FIG. Since the plan view shape of the present modification is substantially the same as that of the first embodiment, it is omitted and the same elements are denoted by the same reference numerals.

  In the present modification, the groove 5 is formed by a two-step press process, whereas the groove part 5 is formed by a single press process in the first embodiment. That is, in the first press work, the first groove 51 (first breaking groove) is formed without reducing the thickness until the predetermined remaining thickness of the thinnest portion is reached. Next, the bottom portion of the first groove portion 51 is pressed to form the second groove portion 52 (second breaking groove) so as to reach a predetermined remaining thickness of the thinnest portion. Therefore, the cross-sectional shape of the groove 5 is a stepped groove as shown in FIG. And since the groove part 5 formed in this way has the small amount of processing by one press work, it becomes easy to process the remaining thickness Ts of the thinnest part with high precision. Note that the remaining thickness Ts and width Ws of the thinnest portion and the distance Ls from the long side of the groove 5 are in accordance with the first embodiment. Further, the remaining thickness and width of the bottom portion of the first groove portion 51 are not particularly limited in accordance with the pressing method or the like.

  Next, an explosion-proof mechanism according to the second embodiment of the present invention will be described with reference to FIG. FIGS. 3A and 3B are schematic views of the explosion-proof mechanism of the second embodiment, in which FIG. 3A is a plan view (a partially enlarged side view of the battery case), and FIG. 3B is a cross-sectional view taken along line BB in FIG. In addition, the same code | symbol is attached | subjected about the element same as 1st Embodiment (refer FIG. 2), and the description is abbreviate | omitted.

  The explosion-proof mechanism 41 of this embodiment is provided in the approximate center of the side surface 32 which is a narrow surface of the main body 3 as in the first embodiment (see FIG. 1A). Then, as shown in FIGS. 3A and 3B, it is composed of a recess 6 having an oval shape in plan view and a groove portion 5 formed substantially inside the recess 6 in a plan view.

  The planar view shape of the recess 6 is preferably a closed curve that is substantially similar to the groove 5 that includes a curve or a part of the curve. This is because the distance Ls ′ of the groove portion 5 from the falling portion of the concave portion 6 is not extremely separated, and when the side surface 32 is bent at the concave portion 6, the groove portion 5 is not detached from the bent line. is there. The distance Ls ′ is not particularly limited, but is preferably 1 mm or less in terms of workability and strength. Further, the distance Ld from the long side of the falling portion of the recess 6 is not particularly limited because it depends on the width of the side surface 32 and the like, but is preferably 0.4 to 1.5 mm from the viewpoint of ease of buckling and workability. It is. Moreover, the depth D of the recessed part 6 is although it does not specifically limit, Preferably it is 0.5-3 mm from the point of the ease of generating buckling and the workability. The angle of the falling portion (side wall) of the concave portion 6 is not particularly limited, but is preferably 80 to 90 ° from the viewpoint of ease of buckling and workability. The recess 6 is preferably formed by pressing such as coining.

  Moreover, about the shape (width | variety and remaining thickness) of the groove part 5, it shall follow the 1st Embodiment. Moreover, you may form the groove part 5 by a two-stage press work like the modification of 1st Embodiment (refer FIG.2 (c)). In the present embodiment, the shape of the groove 5 and the recess 6 in plan view is an ellipse, but the recess 6 may be another closed curve such as an ellipse, a perfect circle, or a rounded square.

  The side surface 32 including the groove portion 5 and the recess portion 6 is unlikely to be deformed with a small load. When the internal pressure increases, the central portion of the side surface 32 is drawn inward, and when the internal pressure further increases, the shoulder portion (falling portion) of the recess 6 is the starting point of buckling, as in the first embodiment. As a result, the side surface 32 bends, and a part of the wide surface in contact with the bent portion buckles, rises into a square shape and deforms. As a result of such non-uniform deformation, the groove 5 that is a thin wall formed inside the recess 6 is easily broken to release the internal pressure. Thus, since the concave portion 6 including the groove portion 5 is a starting point of buckling, the side surface 32 is reliably bent at the position where the groove portion 5 is formed, and is easily broken.

  By being comprised as mentioned above, it can be set as the battery case 1 which the explosion-proof mechanism 4 will tear when a predetermined internal pressure is exceeded. The internal pressure at which the explosion-proof mechanism 4 is cleaved is preferably 0.25 to 0.42 MPa. If the internal pressure exceeds 0.42 MPa, the battery case 1 may be ruptured if it is not cleaved. In addition, the lower limit value of the internal pressure at which the explosion-proof mechanism 4 is cleaved is not particularly limited, but is 0.25 MPa or more in order not to be cleaved by an impact in the manufacturing process or the temporary and small increase in internal pressure during summer use. It is preferable that More preferably, it is 0.35-0.4 MPa in the internal pressure which cleaves. In the first embodiment, the shape of the groove 5 in plan view is an ellipse, but other shapes such as an ellipse, a perfect circle, and a rounded rectangle may be used as long as the curve or a closed curve including a part of the curve is included. However, a discontinuous closed curve such as a C-shape or a U-shape in which a part of these closed curves is discontinuous may be used. This is because in the case of a groove portion having a corner shape such as a rectangle, the groove portion may be damaged at the time of thin-wall processing, and the rigidity of the groove portion is increased by the corner portion, and the internal pressure for cleavage is increased. In the second embodiment, the groove 5 may be a closed curve that is substantially similar to the recess 6 or may be a discontinuous closed curve that lacks a part of the substantially similar closed curve. In addition, when making the groove part 5 into a discontinuous closed curve, it is preferable to form a continuous groove more than half of the original closed curve in both the first and second embodiments.

  Next, an example of the battery case manufacturing method according to the present invention will be described.

  First, the aluminum alloy which comprises the cover 2 and the main body 3 of the battery case 1 is each made into predetermined thickness by a well-known method, and an aluminum alloy plate is obtained. And the lid | cover 2 cut | disconnects an aluminum alloy plate in a defined shape, and forms the hole for a terminal, an injection hole, etc. The main body 3 is formed by cutting an aluminum alloy plate into a predetermined shape and drawing it into a box whose upper surface is opened by drawing or the like.

  Next, a mold is arranged inside and outside the main body 3, and a substantially central portion of the side surface 32 is recessed into a predetermined shape by coining to form a recess 6. Further, another mold is arranged and the groove 5 is formed inside the recess 6 by coining.

  A secondary battery material (a positive electrode material, a negative electrode material, a separator, or the like) is stored in the main body 3, and the lid 2 is joined to the upper surface. And electrolyte solution is inject | poured and an injection hole is sealed and it is set as a secondary battery.

  Next, the process by which the explosion-proof mechanism in the battery case according to the present invention is cleaved will be described with reference to the drawings. FIG. 4 is an external perspective view showing the battery case according to the second embodiment of the present invention in a state where the explosion-proof mechanism is cleaved. FIG. 5 is a plan view for explaining a process in which the explosion-proof mechanism of the battery case according to the second embodiment of the present invention is cleaved, where (a) shows a normal internal pressure, and (b) to (d) show an internal state. A state in which the pressure increases, (e) shows a state in which the pressure is cleaved. 4 and 5 are shown with the front surface (wide surface) facing upward.

  First, when the internal pressure starts to rise, as shown in FIG. 5 (b), the two wide surfaces facing each other swell from the center in a direction away from each other as shown in FIG. 5 (b). At this time, the side surface 32 is drawn to the ridgeline (long side) with both wide surfaces, and the center of the surface is drawn inside (in the drawing back direction). At this time, a side surface (not shown) facing the side surface 32 is also drawn into the inside. When the internal pressure further rises, the center of the side surface 32 is further drawn into the inside, and as shown in FIG. 5C, the falling portion of the concave portion 6 starts to bend into the inside as a buckling start point. At the same time, the wide surface (front surface 31) in contact with the bent portion is also buckled, sharply bent and deformed, and the angular portion 7 is generated. The corner portion 7 and the vicinity thereof are stiffer than the other portions of the wide surface due to steep bent lines. When the internal pressure continues to act on this highly rigid portion, a particularly large tensile stress acts. As a result, a large tensile stress also acts on the portion of the side surface portion 32 near the corner portion 7, that is, the center.

  When the internal pressure further increases, the bending of the side surface 32 increases as shown in FIG. 5D, and the stress acting on the center of the side surface 32 increases with the expansion of the rectangular portion 7 on the front surface 31. As a result, the groove 5 on the bent line is broken (FIG. 5E). Even if the remaining thickness of the groove 5 is not extremely reduced by this stress, the groove 5 can be broken at a relatively low internal pressure. In addition, since the shape of the groove 5 in plan view is a closed curve or a discontinuous closed curve in which a part thereof is discontinuous, there are two grooves (thin wall portions) crossing the bent line of the side surface 32, and the fracture is more reliably performed. . As shown in the perspective view of FIG. 4, the side surface 32 is a central portion where the concave portion 6 and the groove portion 5 are formed, and bends toward the inside of the battery case as compared with the normal state indicated by the two-dot chain line. The front surface 31 is also bent near the side surface 32 to form a horn 7. In addition, in this embodiment, although the square part 7 has arisen in the front surface 31, the same deformation | transformation may arise also in a back surface.

  As described above, the side surface 32 is easily deformed in the vicinity of the center in the longitudinal direction. Further, by providing the concave portion 6, the side surface 32 can be reliably deformed at the position of the groove portion 5. Can also be preferentially deformed.

  Although the best mode for carrying out the present invention has been described above, an example in which the effect of the present invention has been confirmed will be specifically described below in comparison with a comparative example that does not satisfy the requirements of the present invention. . In addition, this invention is not limited to this Example.

(Example)
First, a 3000 series aluminum alloy having a yield strength shown in Table 1 is made into an aluminum alloy plate having a thickness of 0.5 mm, and this is drawn to a thickness of 0.5 mm on the bottom surface, 0.20 mm on the front and back surfaces (wide surface), It was molded into a box body having a side surface (narrow surface) of 0.20 mm and an open top surface. Next, a groove having an elliptical shape with a width of 2.0 mm and a length of 4.0 mm, a width of 80 μm at the thinnest portion, and a remaining thickness as shown in Table 1 is formed at the approximate center of one side surface by coining. Formed as a main body. A lid made of a 3000 series aluminum alloy plate having a thickness of 1 mm was joined to this main body by welding to obtain Example 1. In another box formed in the same manner, after forming a recess having a depth of 1 mm and a length of 3.0 mm and a length of 5.0 mm by coining at the approximate center of one side surface Then, a groove having the same shape as that of Example 1 was formed inside the concave portion to form a main body, and a lid was joined in the same manner as in Example 1 to obtain Examples 2 to 6. The completed Examples 1 to 6 have a rectangular parallelepiped shape having a width of 30 mm, a height of 50 mm, and a depth (width of a narrow surface) of 5 mm, which is almost the same as the specification of a lithium ion secondary battery mounted on a mobile phone. The same thing.

(Comparative example)
In Comparative Examples 1 to 3, an explosion-proof mechanism was formed at the position shown in Table 1, and the other specifications were made with the same specifications as in Example 2.

(Working pressure test)
In the operating pressure test, internal pressure was applied to the battery cases of the example and the comparative example, and the measurement was performed using the pressure at which the groove portion was broken and opened as the operating pressure. The acceptance criteria for the working pressure is 0.25 to 0.42 MPa, and the measurement results are shown in Table 1.

  In Examples 1 to 6, since the formation position of the explosion-proof mechanism is within the range of the present invention, the internal pressure was cleaved at 0.25 to 0.42 MPa. In particular, in Examples 1 and 2, the yield strength of the aluminum alloy of the main body and the remaining thickness of the thinnest portion were preferable values, so that the internal pressure was cleaved at 0.35 to 0.4 MPa. In addition, Example 2 which formed the recessed part in the explosion-proof mechanism was cleaved with the internal pressure a little lower compared with Example 1 without a recessed part. Further, in comparison with these, Example 3 in which the yield strength of the aluminum alloy was low and Example 5 in which the remaining thickness of the thinnest part was thin were cleaved at a low internal pressure. On the other hand, Example 4 in which the yield strength of the aluminum alloy was high and Example 6 in which the remaining thickness of the thinnest portion was thick were cleaved at a high internal pressure.

  In Comparative Example 1, the position where the explosion-proof mechanism was formed was a lid having a thick plate thickness and high internal pressure leading to deformation as compared with the main body, and it was out of the center, so the internal pressure increased 0.42 MPa. Cleaved beyond. Moreover, although the explosion-proof mechanisms of Comparative Examples 2 and 3 are on the side of the main body, they are formed on the side of the lid and the side of the bottom, respectively, so that they are not easily affected by the side surface deformation, and both have an internal pressure exceeding 0.42 MPa. Cleaved.

It is an external appearance perspective view of a battery case, (a) is an external appearance perspective view of the battery case of embodiment of this invention, (b) is an external appearance perspective view of the battery case of another embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of the explosion-proof mechanism of the 1st Embodiment of this invention, (a) is a top view (a side view partial enlarged view of a battery case), (b) is AA sectional drawing of (a), (c). These are sectional drawings of the modification of 1st Embodiment. It is the schematic diagram of the explosion-proof mechanism of the 2nd Embodiment of this invention, (a) is a top view (side view partial enlarged view of a battery case), (b) is BB sectional drawing of (a). It is an external appearance perspective view which shows the state which the battery case which is embodiment of this invention opened. FIG. 6 is a plan view for explaining a process in which the explosion-proof mechanism of the battery case according to the second embodiment of the present invention is cleaved, where (a) shows a normal internal pressure, and (b) to (d) show that the internal pressure increases. (E) is a diagram in a cleaved state.

Explanation of symbols

1,1A battery case 2,2A lid 3,3A body 31,31A body front (wide surface)
32 Body side (narrow surface)
32A bottom surface (narrow surface)
4, 41 Explosion-proof mechanism 5 Groove (broken groove)
51 1st groove (first breaking groove)
52 Second groove (second breaking groove)
6 recess

Claims (6)

A battery case with a sealed structure provided with an explosion-proof mechanism that partially cleaves when the internal pressure rises and exceeds a predetermined value,
The battery case is a flat rectangular parallelepiped whose front and back are wider than the side and bottom, and is composed of a lid formed from the upper surface and a body composed of five surfaces other than the upper surface.
The main body has a rupture groove formed at a substantially center of the side surface or the bottom surface, which is a narrow surface,
The battery case, wherein the breaking groove portion is formed into a closed curve including a curve or a part of a curve, or a discontinuous closed curve in which a part of the closed curve is discontinuous, thereby forming the explosion-proof mechanism.   The battery case according to claim 1, wherein a concave portion surrounding the breaking groove is formed on the side surface or the bottom surface. The breaking groove portion includes a first breaking groove and a second breaking groove formed at the bottom of the first breaking groove,
3. The battery case according to claim 1, wherein a bottom portion of the second breaking groove is a bottom portion of the breaking groove portion.   4. The battery case according to claim 1, wherein the breaking groove portion of the discontinuous closed curve includes a continuous portion at least half of the closed curve. The main body is made of an aluminum alloy plate having a yield strength of 200 to 300 MPa,
The remaining thickness of the thinnest wall portion which is the bottom of the breaking groove portion is 40 to 70 μm,
5. The battery case according to claim 2, wherein when the internal pressure is 0.4 MPa or less, buckling deformation occurs in the concave portion and the breaking groove portion is broken.   6. The battery case according to claim 1, wherein the main body is made of a 3000 series aluminum alloy plate.

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